A large number of patients with both neoplastic and non-neoplastic inappropriate secretion of thyrotropin as well as patients with various degrees of primary hypothyroidism have been evaluated for TSH bioactivity. There is an inverse relationship between the metabolic status of an individual in terms of circulating hormone levels and the biological potency of the TSH. Moreover, patients with TSH-producing pituitary tumors show an increased bioactivity which may be an early marker for the disease. Enzymatic deglycosylation of TSH with peptide N-glycosidase F and endo-Beta-N-acetylglucosaminidase F can be achieved under non-denaturing conditions and will permit analysis of the role of each carbohydrate chain in TSH action.